diff --git a/src/json-validator.cpp b/src/json-validator.cpp
index 54a94c7..8a1e834 100644
--- a/src/json-validator.cpp
+++ b/src/json-validator.cpp
@@ -1163,7 +1163,7 @@ std::shared_ptr<schema> schema::make(json &schema,
 		schema.erase("title");
 		schema.erase("description");
 	} else {
-		return nullptr; // TODO error/throw? when schema is invalid
+		throw std::invalid_argument("invalid JSON-type for a schema for " + uris[0].to_string() + ", expected: boolean or object");
 	}
 
 	for (auto &uri : uris) { // for all URIs this schema is referenced by
diff --git a/test/issue-101/CMakeLists.txt b/test/issue-101/CMakeLists.txt
new file mode 100644
index 0000000..41ad0c9
--- /dev/null
+++ b/test/issue-101/CMakeLists.txt
@@ -0,0 +1,6 @@
+add_test_simple_schema(Issue::101
+                       ${CMAKE_CURRENT_SOURCE_DIR}/schema.json
+                       ${CMAKE_CURRENT_SOURCE_DIR}/instance.json)
+set_tests_properties(Issue::101
+                     PROPERTIES
+                         WILL_FAIL 1)
diff --git a/test/issue-101/instance.json b/test/issue-101/instance.json
new file mode 100644
index 0000000..fb5716b
--- /dev/null
+++ b/test/issue-101/instance.json
@@ -0,0 +1 @@
+{"top": 1}
diff --git a/test/issue-101/schema.json b/test/issue-101/schema.json
new file mode 100644
index 0000000..19fad64
--- /dev/null
+++ b/test/issue-101/schema.json
@@ -0,0 +1,12 @@
+{
+    "$id": "http://xxx.local/schemas/mySchema.json",
+    "$schema": "http://json-schema.org/draft-07/schema#",
+
+    "type": "object",
+    "properties": {
+        "top": {
+            "type": "integer"
+        },
+        "required": ["top"]
+    }
+}